Rebaseline 28 gradient results after r159891.

Unreviewed gardening.

TBR=senorblanco@chromium.org

Review URL: https://codereview.chromium.org/31593002

git-svn-id: svn://svn.chromium.org/blink/trunk@160049 bbb929c8-8fbe-4397-9dbb-9b2b20218538